Local shops may charge a small service fee, but some may refuse the job due to the risk of damaging aged internal ribbons.
If you plan to install it yourself, you will need specific tools often sold in "Fix Kits": buy iphone 4 battery locally
Ensure you buy a battery specifically for the iPhone 4 . The iPhone 4S battery has a connector on the opposite side and is not compatible. Local shops may charge a small service fee,
Stores that focus on vintage electronics or legacy device repairs. buy iphone 4 battery locally
For the two bottom security screws.
Check small electronics repair kiosks in local malls.